The invention is directed to a process for doping semiconductor crystals, particularly those made of silicon by applying a silicon dioxide additive layer containing dropout additive which by subsequent calcining diffuse into the silicon crystals and thereby according to the doping additive used, according to the duration of diffusion and calcining temperature form p- or n-zones of different, but definite, depths of penetration and with a specific, fixed concentration pattern.
There have already been proposed for carrying out such doping processes several types of preparations which are characterized by different layer forming components. In one case there is used for this purpose colloidal SiO.sub.2 which is emulsified in organic solvents together with the doping material. Another preparation utilizes as coating components monosilicon tetra-acetate or monosilicon triacetate with a vinyl group. A further proposal is directed to the use of tetraethyl orthosilicate as coating forming components.
The known doping processes of this type, however, are not sufficiently stable, they flock out after a time of 3 to 6 months as highly viscous materials or gel either through the action of the moisture, which reaches the preparation in repeated opening of the stock flasks, or through internal cross-linking reaction. The thus changed preparations are no longer usable for the described doping process.
If in place of the hydrolysis sensitive coating forming components there are used stable components then it is not possible to use the process in the desired way, i.e. applying a liquid film, which is converted in relatively short time by hydrolysis into a doping material containing silicon dioxide film, since in this case the hydrolysis and the cross-linking reaction only run very slowly or do not start at all.
Therefore it was the problem of the present invention to find a process for doping semiconductor crystals, especially silicon semiconductor crystals, using a solution which contains a silicon dioxide film forming material, n- or p-doping material and organic solvent whereby the film forming material should make possible a sufficient storage stability of the solution and on the other hand after applying on the semiconductor crystal make possible the building of a cohesive silicon dioxide film by the effects of air moisture and connected heating.